feat: freestanding support added

Resolves #564, #565, and #556

src/CMakeLists.txt

@@ -42,6 +42,9 @@ message(STATUS "${projectPrefix}BUILD_AS_SYSTEM_HEADERS: ${${projectPrefix}BUILD
 option(${projectPrefix}BUILD_CXX_MODULES "Add C++ modules to the list of default targets" OFF)
 message(STATUS "${projectPrefix}BUILD_CXX_MODULES: ${${projectPrefix}BUILD_CXX_MODULES}")
 
+option(${projectPrefix}API_FREESTANDING "Builds only freestanding part of the library" OFF)
+message(STATUS "${projectPrefix}API_FREESTANDING: ${${projectPrefix}API_FREESTANDING}")
+
 if(${projectPrefix}BUILD_AS_SYSTEM_HEADERS)
     set(${projectPrefix}_AS_SYSTEM SYSTEM)
 endif()
@@ -71,6 +74,10 @@ cache_var_values(API_NO_CRTP AUTO TRUE FALSE)
 set(${projectPrefix}API_CONTRACTS GSL-LITE CACHE STRING "Enable contract checking")
 cache_var_values(API_CONTRACTS NONE GSL-LITE MS-GSL)
 
+if(${projectPrefix}API_FREESTANDING AND NOT ${projectPrefix}API_CONTRACTS STREQUAL "NONE")
+    message(FATAL_ERROR "'${projectPrefix}API_CONTRACTS' should be set to 'NONE' for a freestanding build")
+endif()
+
 # C++ features
 check_cxx_feature_supported(__cpp_lib_format ${projectPrefix}LIB_FORMAT_SUPPORTED)
 check_cxx_feature_supported("__cpp_constexpr >= 202211L" ${projectPrefix}STATIC_CONSTEXPR_VARS_IN_CONSTEXPR_FUNCTIONS)

src/core/CMakeLists.txt

@@ -35,7 +35,6 @@ endfunction()
 add_mp_units_module(
     core mp-units-core
     HEADERS include/mp-units/bits/core_gmf.h
-            include/mp-units/bits/fmt.h
             include/mp-units/bits/get_associated_quantity.h
             include/mp-units/bits/get_common_base.h
             include/mp-units/bits/hacks.h
@@ -73,14 +72,27 @@ add_mp_units_module(
             include/mp-units/framework/value_cast.h
             include/mp-units/compat_macros.h
             include/mp-units/concepts.h
-            include/mp-units/format.h
             include/mp-units/framework.h
-            include/mp-units/math.h
-            include/mp-units/ostream.h
-            include/mp-units/random.h
     MODULE_INTERFACE_UNIT mp-units-core.cpp
 )
 
+if(NOT ${projectPrefix}API_FREESTANDING)
+    target_sources(
+        mp-units-core
+        PUBLIC FILE_SET
+               HEADERS
+               BASE_DIRS
+               ${CMAKE_CURRENT_SOURCE_DIR}/include
+               FILES
+               include/mp-units/bits/fmt.h
+               include/mp-units/bits/requires_hosted.h
+               include/mp-units/math.h
+               include/mp-units/ostream.h
+               include/mp-units/format.h
+               include/mp-units/random.h
+    )
+endif()
+
 set_feature_flag(API_STD_FORMAT)
 set_feature_flag(API_STRING_VIEW_RET)
 set_feature_flag(API_NO_CRTP)
@@ -133,4 +145,8 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     )
 endif()
 
-# target_compile_options(mp-units-core ${${projectPrefix}TARGET_SCOPE} "-ftime-trace")
+# Freestanding
+target_compile_definitions(
+    mp-units-core ${${projectPrefix}TARGET_SCOPE}
+                  ${projectPrefix}HOSTED=$<NOT:$<BOOL:${${projectPrefix}API_FREESTANDING}>>
+)

src/core/include/mp-units/bits/core_gmf.h

@@ -25,7 +25,6 @@
 #include <mp-units/bits/hacks.h>
 #include <mp-units/compat_macros.h>
 #include <array>
-#include <cmath>
 #include <compare>
 #include <concepts>
 #include <cstddef>
@@ -35,18 +34,23 @@
 #include <initializer_list>
 #include <iterator>
 #include <limits>
-#include <locale>
 #include <numbers>
 #include <numeric>
 #include <optional>
-#include <random>
-#include <sstream>
-#include <string>
+#include <ranges>
 #include <string_view>
 #include <tuple>
 #include <type_traits>
 #include <utility>
 
+#if MP_UNITS_HOSTED
+#include <cmath>
+#include <locale>
+#include <ostream>
+#include <random>
+#include <sstream>
+#include <string>
+
 #if MP_UNITS_USE_FMTLIB
 MP_UNITS_DIAGNOSTIC_PUSH
 MP_UNITS_DIAGNOSTIC_IGNORE_UNREACHABLE
@@ -57,6 +61,8 @@ MP_UNITS_DIAGNOSTIC_POP
 #include <format>
 #endif
 
+#endif
+
 #if __cpp_lib_text_encoding
 #include <text_encoding>
 #endif

src/core/include/mp-units/bits/hacks.h

@@ -73,6 +73,10 @@
 #define MP_UNITS_DIAGNOSTIC_IGNORE_DEPRECATED
 #endif
 
+#if !defined MP_UNITS_HOSTED && defined __STDC_HOSTED__
+#define MP_UNITS_HOSTED __STDC_HOSTED__
+#endif
+
 #if MP_UNITS_COMP_MSVC
 
 #define MP_UNITS_TYPENAME typename

src/core/include/mp-units/bits/requires_hosted.h

@@ -0,0 +1,29 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <mp-units/bits/hacks.h>
+
+#if !MP_UNITS_HOSTED
+#error "This header is not available in freestanding mode."
+#endif

src/core/include/mp-units/bits/text_tools.h

@@ -23,6 +23,7 @@
 #pragma once
 
 #include <mp-units/bits/ratio.h>
+#include <mp-units/compat_macros.h>
 #include <mp-units/ext/fixed_string.h>
 #include <mp-units/ext/type_traits.h>
 #include <mp-units/framework/symbol_text.h>
@@ -100,12 +101,12 @@ constexpr Out copy(const symbol_text<N, M>& txt, text_encoding encoding, Out out
       for (const char8_t ch : txt.unicode()) *out++ = static_cast<char>(ch);
       return out;
     } else
-      throw std::invalid_argument("Unicode text can't be copied to CharT output");
+      MP_UNITS_THROW(std::invalid_argument("Unicode text can't be copied to CharT output"));
   } else {
     if constexpr (is_same_v<CharT, char>)
       return ::mp_units::detail::copy(txt.ascii().begin(), txt.ascii().end(), out);
     else
-      throw std::invalid_argument("ASCII text can't be copied to CharT output");
+      MP_UNITS_THROW(std::invalid_argument("ASCII text can't be copied to CharT output"));
   }
 }
 

src/core/include/mp-units/compat_macros.h

@@ -40,6 +40,15 @@
 
 #endif
 
+#if MP_UNITS_HOSTED
+#define MP_UNITS_THROW(expr) throw expr
+#else
+#include <cstdlib>
+#define MP_UNITS_THROW(expr) std::abort()
+#endif
+
+#if MP_UNITS_HOSTED
+
 #if defined MP_UNITS_API_STD_FORMAT && !MP_UNITS_API_STD_FORMAT
 
 #define MP_UNITS_USE_FMTLIB 1
@@ -59,21 +68,7 @@
 #define MP_UNITS_FMT_TO_ARG_ID(arg) (arg)
 #define MP_UNITS_FMT_FROM_ARG_ID(arg) (arg)
 
-// This re-uses code from fmt;
-#if FMT_EXCEPTIONS
-#if FMT_MSC_VERSION || defined(__NVCC__)
-#define MP_UNITS_THROW(x) ::fmt::detail::do_throw(x)
-#else
-#define MP_UNITS_THROW(x) throw x
-#endif
-#else
-#define MP_UNITS_THROW(x)          \
-  do {                             \
-    FMT_ASSERT(false, (x).what()); \
-  } while (false)
-#endif
-
-#else
+#else  // MP_UNITS_USE_FMTLIB
 
 #if !defined __cpp_lib_format && !defined MP_UNITS_COMP_CLANG
 #error "std::formatting facility not supported"
@@ -83,10 +78,8 @@
 #define MP_UNITS_FMT_LOCALE(loc) loc
 #define MP_UNITS_FMT_TO_ARG_ID(arg) static_cast<std::size_t>(arg)
 #define MP_UNITS_FMT_FROM_ARG_ID(arg) static_cast<int>(arg)
-#define MP_UNITS_THROW(arg) throw arg
-
-#endif
 
+#endif  // MP_UNITS_USE_FMTLIB
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 
@@ -104,6 +97,8 @@ MP_UNITS_DIAGNOSTIC_POP
 
 #endif
 
+#endif  // MP_UNITS_HOSTED
+
 #if MP_UNITS_API_CONTRACTS == 2 || __has_include(<gsl/gsl-lite.hpp>)
 
 #include <gsl/gsl-lite.hpp>

src/core/include/mp-units/ext/fixed_string.h

@@ -35,8 +35,11 @@
 #include <compare>  // IWYU pragma: export
 #include <cstddef>
 #include <cstdlib>
-#include <ostream>
+#include <ranges>
 #include <string_view>
+#if MP_UNITS_HOSTED
+#include <ostream>
+#endif
 #endif
 
 MP_UNITS_EXPORT
@@ -123,11 +126,14 @@ public:
     return data()[pos];
   }
 
+#if MP_UNITS_HOSTED
   [[nodiscard]] constexpr const_reference at(size_type pos) const
   {
     if (pos >= size()) throw std::out_of_range("basic_fixed_string::at");
     return (*this)[pos];
   }
+#endif
+
   [[nodiscard]] constexpr const_reference front() const
   {
     MP_UNITS_EXPECTS(!empty());
@@ -239,11 +245,13 @@ public:
   }
 
   // inserters and extractors
+#if MP_UNITS_HOSTED
   friend std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os,
                                                        const basic_fixed_string& str)
   {
     return os << str.c_str();
   }
+#endif
 };
 
 // deduction guides
@@ -282,6 +290,7 @@ struct std::hash<mp_units::fixed_u32string<N>> : std::hash<std::u32string_view>
 template<std::size_t N>
 struct std::hash<mp_units::fixed_wstring<N>> : std::hash<std::wstring_view> {};
 
+#if MP_UNITS_HOSTED
 // formatting support
 template<typename CharT, std::size_t N>
 struct MP_UNITS_STD_FMT::formatter<mp_units::basic_fixed_string<CharT, N>> : formatter<std::basic_string_view<CharT>> {
@@ -291,4 +300,6 @@ struct MP_UNITS_STD_FMT::formatter<mp_units::basic_fixed_string<CharT, N>> : for
     return formatter<std::basic_string_view<CharT>>::format(std::basic_string_view<CharT>(str), ctx);
   }
 };
+#endif
+
 // NOLINTEND(*-avoid-c-arrays)

src/core/include/mp-units/format.h

@@ -24,6 +24,8 @@
 
 #pragma once
 
+#include <mp-units/bits/requires_hosted.h>
+//
 #include <mp-units/bits/fmt.h>
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/compat_macros.h>

src/core/include/mp-units/framework/dimension.h

@@ -37,8 +37,10 @@
 #include <array>
 #include <cstdint>
 #include <iterator>
-#include <string>
 #include <string_view>
+#if MP_UNITS_HOSTED
+#include <string>
+#endif
 #endif
 
 namespace mp_units {
@@ -318,9 +320,15 @@ MP_UNITS_EXPORT template<dimension_symbol_formatting fmt = dimension_symbol_form
 #endif
 {
   auto get_size = []() consteval {
+#if MP_UNITS_HOSTED
     std::basic_string<CharT> buffer;
     dimension_symbol_to<CharT>(std::back_inserter(buffer), D{}, fmt);
     return buffer.size();
+#else
+    std::array<CharT, 128> buffer;  // TODO unsafe
+    auto end = dimension_symbol_to<CharT>(buffer.begin(), D{}, fmt);
+    return end - buffer.begin();
+#endif
   };
 
 #if MP_UNITS_API_STRING_VIEW_RET  // Permitting static constexpr variables in constexpr functions

src/core/include/mp-units/framework/unit.h

@@ -44,8 +44,10 @@
 #include <array>
 #include <cstdint>
 #include <iterator>
-#include <string>
 #include <string_view>
+#if MP_UNITS_HOSTED
+#include <string>
+#endif
 #endif
 
 namespace mp_units {
@@ -718,8 +720,8 @@ constexpr Out print_separator(Out out, const unit_symbol_formatting& fmt)
 {
   if (fmt.separator == unit_symbol_separator::half_high_dot) {
     if (fmt.encoding != text_encoding::unicode)
-      throw std::invalid_argument(
-        "'unit_symbol_separator::half_high_dot' can be only used with 'text_encoding::unicode'");
+      MP_UNITS_THROW(
+        std::invalid_argument("'unit_symbol_separator::half_high_dot' can be only used with 'text_encoding::unicode'"));
     const std::string_view dot = "⋅";
     out = detail::copy(dot.begin(), dot.end(), out);
   } else {
@@ -844,9 +846,15 @@ MP_UNITS_EXPORT template<unit_symbol_formatting fmt = unit_symbol_formatting{},
 #endif
 {
   auto get_size = []() consteval {
+#if MP_UNITS_HOSTED
     std::basic_string<CharT> buffer;
     unit_symbol_to<CharT>(std::back_inserter(buffer), U{}, fmt);
     return buffer.size();
+#else
+    std::array<CharT, 128> buffer;  // TODO unsafe
+    auto end = unit_symbol_to<CharT>(buffer.begin(), U{}, fmt);
+    return end - buffer.begin();
+#endif
   };
 
 #if MP_UNITS_API_STRING_VIEW_RET  // Permitting static constexpr variables in constexpr functions

src/core/include/mp-units/math.h

@@ -22,6 +22,8 @@
 
 #pragma once
 
+#include <mp-units/bits/requires_hosted.h>
+//
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/framework/customization_points.h>
 #include <mp-units/framework/quantity.h>

src/core/include/mp-units/ostream.h

@@ -23,6 +23,8 @@
 
 #pragma once
 
+#include <mp-units/bits/requires_hosted.h>
+//
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/framework/quantity.h>
 #include <mp-units/framework/unit.h>

src/core/mp-units-core.cpp

@@ -8,8 +8,11 @@ export module mp_units.core;
 
 #include <mp-units/compat_macros.h>
 #include <mp-units/concepts.h>
-#include <mp-units/format.h>
 #include <mp-units/framework.h>
+
+#if MP_UNITS_HOSTED
+#include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/ostream.h>
 #include <mp-units/random.h>
+#endif

src/systems/CMakeLists.txt

@@ -25,8 +25,7 @@ cmake_minimum_required(VERSION 3.23)
 add_mp_units_module(
     systems mp-units-systems
     DEPENDENCIES mp-units::core
-    HEADERS include/mp-units/systems/angular/math.h
-            include/mp-units/systems/angular/units.h
+    HEADERS include/mp-units/systems/angular/units.h
             include/mp-units/systems/iec80000/binary_prefixes.h
             include/mp-units/systems/iec80000/quantities.h
             include/mp-units/systems/iec80000/unit_symbols.h
@@ -39,9 +38,7 @@ add_mp_units_module(
             include/mp-units/systems/isq/si_quantities.h
             include/mp-units/systems/isq/space_and_time.h
             include/mp-units/systems/isq/thermodynamics.h
-            include/mp-units/systems/si/chrono.h
             include/mp-units/systems/si/constants.h
-            include/mp-units/systems/si/math.h
             include/mp-units/systems/si/prefixes.h
             include/mp-units/systems/si/unit_symbols.h
             include/mp-units/systems/si/units.h
@@ -60,3 +57,17 @@ add_mp_units_module(
             include/mp-units/systems/usc.h
     MODULE_INTERFACE_UNIT mp-units-systems.cpp
 )
+
+if(NOT ${projectPrefix}API_FREESTANDING)
+    target_sources(
+        mp-units-systems
+        PUBLIC FILE_SET
+               HEADERS
+               BASE_DIRS
+               ${CMAKE_CURRENT_SOURCE_DIR}/include
+               FILES
+               include/mp-units/systems/angular/math.h
+               include/mp-units/systems/si/math.h
+               include/mp-units/systems/si/chrono.h
+    )
+endif()

src/systems/include/mp-units/systems/angular.h

@@ -23,7 +23,9 @@
 #pragma once
 
 // IWYU pragma: begin_exports
+#if MP_UNITS_HOSTED
 #include <mp-units/systems/angular/math.h>
+#endif
 #include <mp-units/systems/angular/units.h>
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE

src/systems/include/mp-units/systems/angular/math.h

@@ -22,6 +22,8 @@
 
 #pragma once
 
+#include <mp-units/bits/requires_hosted.h>
+//
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/systems/angular/units.h>
 

src/systems/include/mp-units/systems/si.h

@@ -23,9 +23,11 @@
 #pragma once
 
 // IWYU pragma: begin_exports
+#if MP_UNITS_HOSTED
 #include <mp-units/systems/si/chrono.h>
-#include <mp-units/systems/si/constants.h>
 #include <mp-units/systems/si/math.h>
+#endif
+#include <mp-units/systems/si/constants.h>
 #include <mp-units/systems/si/prefixes.h>
 #include <mp-units/systems/si/unit_symbols.h>
 #include <mp-units/systems/si/units.h>

src/systems/include/mp-units/systems/si/chrono.h

@@ -22,6 +22,8 @@
 
 #pragma once
 
+#include <mp-units/bits/requires_hosted.h>
+//
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/systems/isq/si_quantities.h>
 #include <mp-units/systems/si/prefixes.h>

src/systems/include/mp-units/systems/si/math.h

@@ -22,6 +22,8 @@
 
 #pragma once
 
+#include <mp-units/bits/requires_hosted.h>
+//
 #include <mp-units/bits/module_macros.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/units.h>